Due to actualization of environmental problems in recent years, hybrid cars and electric cars have spread. Further, as an air-conditioning device which is applicable to such a vehicle, there has been developed an air-conditioning device which includes a compressor to compress and discharge a refrigerant, a radiator (a condenser) disposed in a vehicle interior air flow passage to let the refrigerant radiate heat, a heat absorber (an evaporator) disposed in the vehicle interior air flow passage to let the refrigerant absorb heat, and an outdoor heat exchanger disposed outside a vehicle interior to let the refrigerant absorb heat, and which lets the refrigerant discharged from the compressor radiate heat in the radiator, decompresses the refrigerant by which heat has been radiated by an outdoor expansion valve, and then lets the refrigerant absorb heat in the outdoor heat exchanger to heat air to be supplied from an indoor blower (a blower fan), thereby heating the vehicle interior (e.g., see Patent Document 1).
Furthermore, in Patent Document 1, there is provided a constitution where a heater core (auxiliary heating means) through which engine cooling water (warm water) circulates is disposed in the vehicle interior air flow passage, and in addition to the heating by the radiator, the heater core also exerts a heating capability. It is to be noted that there is also a case of driving an engine for power generation in the hybrid car, but also in this case, the engine cooling water (the warm water) circulates through the heater core.